Fix parsing of the --storage-driver option
Fix parsing of the --storage-driver option

In the CLI tool, that's a string flag, not a boolean.

Signed-off-by: Nalin Dahyabhai <f562fcb2a0b898bf0be1afc867ea92325d8f825f@redhat.com>

TomSweeneyRedHat/buildah,nalind/buildah-1,projectatomic/buildah,nalind/buildah-1,TomSweeneyRedHat/buildah,ipbabble/buildah,ipbabble/buildah,nalind/buildah-1,nalind/buildah,rhatdan/buildah,nalind/buildah,rhatdan/buildah,TomSweeneyRedHat/buildah,rhatdan/buildah,projectatomic/buildah,projectatomic/buildah